The Patterns and Causes of Dermatitis in Terrestrial and Semi-Aquatic Mammalian Wildlife
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animals
Review
The Patterns and Causes of Dermatitis in Terrestrial and
Semi-Aquatic Mammalian Wildlife
Elise M. Ringwaldt * , Barry W. Brook , Scott Carver and Jessie C. Buettel
School of Natural Sciences, University of Tasmania, Hobart, TAS 7000, Australia;
Barry.Brook@utas.edu.au (B.W.B.); Scott.Carver@utas.edu.au (S.C.); Jessie.Buettel@utas.edu.au (J.C.B.)
* Correspondence: Elise.Ringwaldt@utas.edu.au
Simple Summary: Dermatitis is recognized to manifest from a variety of causes in humans and
animals, but these have never been synthesized for wildlife. We document the causes and investigate
the magnitude of skin diseases and disorders which manifest as, and are described as, dermatitis
in the published literature. Our aim was to identify the major causal agents in the development
of dermatitis, and if certain mammalian wildlife groups or captivity status was a precursor for
the development of dermatitis. The most common causes of dermatitis identified were mites,
bacteria, and fungus, and were more frequently reported for wildlife species within Carnivora and
Artiodactyla. Furthermore, associated with genetic and behavioral variables, some threatened species
were more likely to exhibit dermatitis in captivity. This study provides insight into wild mammalian
species that may be more susceptible to dermatological diseases and discusses the patterns of causes
within wild mammals.
Abstract: Causative disease and stress agents which manifest as dermatitis in mammals have varying
effects on individual animals, from benign irritation and inflammation, to causing morbidity and
Citation: Ringwaldt, E.M.; Brook, even mortality. Bacteria, viruses and ectoparasites are all potential causes of dermatitis, and it can
B.W.; Carver, S.; Buettel, J.C. The
be exacerbated by various environmental, genetic and social factors. Furthermore, it is uncertain
Patterns and Causes of Dermatitis in
whether dermatitis is more likely to manifest in already-vulnerable wildlife species. Here, we
Terrestrial and Semi-Aquatic
systematically review the literature for reports of dermatitis in terrestrial and semi-aquatic wild
Mammalian Wildlife. Animals 2021,
mammalian species, with the goal of determining the biogeographical scale of dermatitis reports, the
11, 1691. https://doi.org/10.3390/
ani11061691
causes of dermatitis, and whether manifestation of dermatitis is reported more commonly in certain
wildlife species or their captivity status (i.e., free-living, in captivity or in a laboratory). We reveal
Academic Editor: Nicole Gottdenker biases in the reporting of dermatitis by a biogeographic realm, with 55% of cases reported in the
Nearctic, and towards particular orders of mammals, namely Artiodactyla and Carnivora. Overall,
Received: 17 May 2021 free-living wildlife is almost twice as likely to be reported as having dermatitis than individuals in
Accepted: 3 June 2021 captivity and six times more likely than individuals in laboratories, which we interpret as owing
Published: 6 June 2021 to exposure to a broader spectrum of parasites in free-ranging individuals, and potential reporting
bias in captive individuals. Notably, dermatitis was reported in 23 threatened species, with some
Publisher’s Note: MDPI stays neutral species more likely than others to be reported exhibiting clinical signs of dermatitis resulting from
with regard to jurisdictional claims in
underlying health problems. We also find that threatened species are more likely to be reported
published maps and institutional affil-
as having dermatitis in captivity, particularly outside of their endemic home range. This review
iations.
highlights diverse patterns of dermatological disease causes in captive and free-ranging wildlife,
conditions under which they are more likely to be documented, and the need for cross-disciplinary
research to ascertain (and so better manage) the varied causes.
Copyright: © 2021 by the authors.
Keywords: captivity; dermatitis; dermatophilosis; exudative dermatitis; free-living; mammal; threat-
Licensee MDPI, Basel, Switzerland.
ened species; wildlife
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
Animals 2021, 11, 1691. https://doi.org/10.3390/ani11061691 https://www.mdpi.com/journal/animalsAnimals 2021, 11, 1691 2 of 19
1. Introduction
Dermatitis is a general term for describing different forms of skin irritation and
inflammation in humans and animals, with some causes of dermatitis being zoonotic and
transmissible between people, domestic or captive animals and wildlife [1,2]. Dermatitis
in humans and animals has been associated with reduced quality of life [3,4] and reports
of dermatitis in threatened species indicates that skin diseases can also be a threat to
persistence [5]. Dermatitis is the term for inflammation of the skin, which can have
many different possible causes [2]. The development of clinical signs of dermatitis can be
due to health issues such as infectious agents, ectoparasites, environmental irritants, or
unknown [6,7]. Research into the cause and treatment of dermatitis has focused on either
human health (e.g., [8,9]), or domestic animals and livestock (e.g., [10]). For some wildlife
species, including many of conservation concern, the etiological agent or mechanisms
behind dermatitis origins are unclear (e.g., [11,12]). The etiological agents which can trigger
dermatitis may cause different effects in individuals; however, the question of whether
there are patterns to the formation of dermatitis clinical signs for diseases or irritants across
wildlife has yet to be determined.
Clinically, there are different types of dermatitis that can be detected by physical
examination, sampling techniques (e.g., skin swabbing, skin scrapings, UV light), or may
require histological examination of tissues [13]. Following detection of dermal lesions, a
common challenge is identifying the causal agent(s). This is because the causes of dermatitis
are variable and can also be species specific, for instance, grey squirrels (Sciurus carolinensis)
do not display clinical signs to the parapoxvirus but spread it to red squirrels (Sciurus
vulgaris) where it, by contrast, causes exudative dermatological lesions [12,14]. Even within
the same species, dermatitis can manifest in a range of ways, from benign, moderate (e.g.,
hair loss), to severe (e.g., ulcerative pustules and necrosis) and mortality causing [5,15].
Benign dermatitis lesions can also lead to secondary infections through self-trauma or
exposure to opportunistic pathogens [16–18].
Historically, research has primarily focused on wildlife exhibiting dermatitis acting as
reservoirs for the pathogen, potentially spilling over into livestock and causing economic
losses in agriculture animals, or transmission to humans due to proximity [1,2,10,19].
However, more recently, due to the increasing recognition of the role of infectious disease
in the modern biodiversity crisis, some skin diseases, with dermatitis as an important
clinical sign, such as Sarcoptic mange and White Nose Syndrome, have been viewed as
an additional conservation pressure on already-threatened species [20–23]. Furthermore,
it is unclear if there are generalities to the onset and progression of the clinical signs of
dermatitis as a manifestation of skin disease across taxa.
The occurrence of dermatitis in wildlife species is global, and, from an animal ethics
perspective, morbidity and mortality from secondary skin infections can be an incontro-
vertible wildlife management issue [10,24]. Dermatitis has been reported in mammalian
wildlife which are already of conservation concern (e.g., [25–27]) and in some cases animals
have died with severe dermatitis or secondary infections [28]. Within the last 10 years,
the specific term ‘exudative dermatitis’ has been used as a common descriptive symptom
in wildlife reports (e.g., [12,29]) and is a type of emerging dermatitis in some Australian
wildlife [30,31]. Therefore, investigating whether specific types of mammalian wildlife are
more likely to be reported as showing dermatitis as a manifestation of disease, and due to
which causal agent, may aid in understanding skin disease risks.
In this review, we aim to consolidate the literature of terrestrial and semi-aquatic
mammalian wildlife that are reported to exhibit dermatitis: firstly, to explore whether
reports of dermatitis are more likely for types of etiological agents; and, secondly, whether
documentation of dermatitis is similar across mammalian wildlife groups or reported more
often in some orders. Additionally, we also identify biases in the reporting of dermatitis,
and investigate threatened species reported as suffering from dermatitis as an added
pressure for species already subjected to environmental and anthropogenic threats. We
attempt to be exhaustive in our search of published reports of dermatitis in the literature,Animals 2021, 11, 1691 3 of 19
and results herein broadly align with general perceptions across a range of texts and sources.
We recognize not all cases fitting the definition are always explicitly termed ‘dermatitis’ in
wildlife, and thus do not claim this review to cover every possible study encompassing
dermatitis symptoms (which we discuss), but we have reasons to be confident that this
review captures general patterns and is thus an appropriate synthesis contributing a general
understanding of this condition in wildlife.
2. Database Search and Literature Screening
To identify the relevant literature, we searched three databases in December 2019 and
additionally in March 2021: Web of Science, Scopus and Google Scholar using the search
string in the topic of: title, abstract and key words, ‘“dermatitis” OR “exudative dermatitis”
AND “wildlife”’ (Search terms S1). We imported all records from Web of Science and
Scopus, and the first-100 papers (ranked-by-relevance) were exported from Google Scholar
for screening to reduce disparate articles (Figure 1). We restricted our literature review
to peer-reviewed publications—as the most robust and defendable source of reports—
available in these most widely used and publicly available databases to researchers. We
acknowledge that this will preclude some non-journal literature (e.g., annual reports,
conference proceedings, books) available in less widely available databases, such as CAB,
which may contain additional reports that could be considered in future analyses.
After duplicate articles were removed, articles were first screened by title and abstract
for relevance to dermatitis and wildlife and those not meeting the inclusion criteria were
removed (Figure 1). We then assessed the full text of the filtered list of articles to identify
records that fit our eligibility criteria. We only included articles which described anywhere
in text, signs of histopathological or superficial dermatitis affecting the mammal in question.
To ensure comprehensiveness of the literature search, we also screened the bibliographies
and reference lists from the final full-text articles (Figure 1).
2.1. Inclusion and Exclusion Criteria
All articles were included in this review if they focused on wild (terrestrial or semi-
aquatic) mammals that reported physical lesions that were diagnosed as dermatitis (re-
gardless of the cause). Articles in this review only included records of mammals exhibiting
dermatological clinical signs, and, therefore, manuscripts which focused exclusively on
serological surveys of pathogens/antibodies which may cause dermatitis were excluded.
Articles were also excluded if the focus of the research was a review, conference proceed-
ings, or book review. After the screening process, articles were also excluded if they only
used data from a previously published study.
2.2. Data Extraction
For each article, we extracted numeric, categorical, and written information about
the manuscript, mammal species exhibiting dermatitis, and the agent causing dermatitis
(Table 1; Table S2).
Table 1. Article Data Extraction: for each article, we collected information on the manuscript, the
individuals per species, and the dermatitis exhibited by each species.
Manuscript Mammal (Per Species) Dermatitis (Per Species)
Title Number of individuals Type
Author(s) Captivity status Location of dermatitis
Year Country Clinical signs
Journal Conservation status Definitive Cause
Key termsAnimals 2021, 11, 1691 4 of 19
Animals 2021, 11, x 4 of 20
Figure 1. Protocol for screening articles after data base search of “dermatitis” OR “exudative dermatitis” AND “wildlife”.
“wildlife”.
Each step shows the number of papers included or excluded for review.
Each step shows the number of papers included or excluded for review.
For articles
After witharticles
duplicate multiplewere species, we recorded
removed, articlesdata
wereforfirst
all individuals
screened byexhibiting
title and
signs of dermatitis.
abstract for relevance When more than and
to dermatitis one species
wildlifeofand
mammal
those was studied, we
not meeting the separated
inclusion
each species
criteria record and,
were removed therefore,
(Figure 1). Wesome papers are
then assessed therepresented more
full text of the thanlist
filtered once for the
of articles
species-specific
to analyses.
identify records that Wefit included data oncriteria.
our eligibility the animal’s
We captivity status, whether
only included it was
articles which
free-living,anywhere
described captive (i.e.,
in contained
text, signsinside a boarder such as
of histopathological orasuperficial
zoo or wildlife park oraffecting
dermatitis reserve),
or laboratory
the mammal in (i.e., a wild To
question. species
ensureto comprehensiveness
be used for laboratory experiments).
of the To determine
literature search, we also
the total number
screened of dermatitis
the bibliographies and cases, for each
reference listspaper, we split
from the final the data by
full-text species
articles reported
(Figure 1).
(n = 244 individual species cases of dermatitis), then by the cause of dermatitis (n = 253Animals 2021, 11, 1691 5 of 19
differential cases of dermatitis), and, finally, by the individual mammals’ captivity status
(n = 257 cases). We also recorded the diagnosed type of dermatitis for each species in the
article (e.g., exudative dermatitis, ulcerative dermatitis) as well as whether the dermatitis
had a definitive causal agent identified (e.g., virus, bacteria, fungus, ectoparasite). If the
causal agent of the dermatitis was not found, we classed the cause as ‘unknown’.
The country for each dermatitis case was documented and each was aggregated
into their corresponding biogeographic realms (also known as ecozones). The World
Wildlife Fund classification of biogeographical realms [32,33] has eight ecozones, being
the broadest biogeographic division of all terrestrial ecosystems on Earth. These are
delineated by broad geographical features, such as oceans and mountain ranges which
have, over time, segregated evolving organisms. Therefore, biogeographic realms are based
on zoogeography evolutionary histories, ecoregions, and phytogeography, among many
other classification systems [33].
Species were updated to their current scientific name if it changed since the article was
published (e.g., Thalarctos maritimus to Ursus maritimus), or, if a subspecies was recorded, we
aggregated under the species name. We grouped species to higher taxa for further analyses
based on the types of dermatitis affecting similar wildlife, as follows: Artiodactyla, even-
toed ungulates (24 species); we split Carnivora into two groups, semi-aquatic Carnivora
(represented by five species of sea lions and seals from the family Otariidae and Phocidae),
and terrestrial Carnivora (20 species including felids, canids, and ursids); Diprotodontia,
marsupial mammals (14 species); Primates, non-human eutherian mammals (nine species);
and Rodentia, rodents (11 species). Five other orders had 10 or less dermatitis diagnoses
and fewer than five species within the grouping. Their individual syntheses are produced in
supplementary tables (Table S3): Didelphimorphia, represented by two species of opossum;
Eulipotyphla, represented by four species of hedgehog; Lagomorpha, hare and rabbit (four
species); Perissodactyla, rhinoceros (three species); Chiroptera, represented by four species
of bat from the family Vespertilionidae. Finally, four unique species did not belong to any
former (broader) order noted above: Elephas maximus (Asian elephant), Ornithorhynchus
anatinus (platypus), Procavia capensis (rock hyrax), and Zaedyus pichiy (pichi) (Table S3).
We used the International Union for Conservation of Nature’s Red List (hereafter
IUCN) (2021) to rank each species via their threat level [34]: Not Evaluated, Data Deficient,
Least Concern, Near Threatened, Vulnerable, Endangered, Critically Endangered, Extinct
in the Wild and Extinct. We also used this as a tool to rank the species with reported
dermatitis cases by global conservation status.
3. Overall Causes, Captivity Status, and Geographic Spread of Reported Dermatitis
Dermatitis in wildlife was reported in 216 papers (1925–2021), totaling 257 dermatitis
cases reported for terrestrial and semi-aquatic wildlife mammals (Table S2). There were 17
definitive causes (and another group for unknown) of dermatitis in wildlife, representing
76.4% of all cases (Table 2). The highest single proportion of dermatitis cases were of an
unknown cause (23.7%, n = 61), followed closely by mites (21.4%, n = 55) and then both
bacteria (16.3%, n = 42) and viruses (16.3%, n = 42) (Table 2). Mites as the causative agent
were found across the highest number of unique wildlife species (34 species), followed by
bacteria (29 species) and then both viruses and fugus (15 species) (Table 2).
Dermatitis was reported in 108 different mammal species, totaling 4118 individuals.
Wild, free-living mammals had a higher frequency of reported dermatitis cases (57.2%,
n = 147, 69 species), compared to wild animals that were brought into or born in captivity
(33.07%, n = 85, 51 species), and those under laboratory conditions (9.73%, n = 25, 12 species)
(Figure 2). The highest proportion of reported cases of dermatitis for free-living wildlife
was caused by mites (Figure 2). By contrast, unknown causes of dermatitis in captive
wildlife had the highest proportion of cases. Interestingly, wildlife from a laboratory setting
had no ‘other’ causes, and the primary cause of dermatitis was unknown (Figure 2).Animals 2021, 11, 1691 6 of 19
Table 2. Overall proportion of causes of dermatitis in terrestrial and semi-aquatic mammalian wildlife.
This shows the cause of dermatitis, the diagnosis proportion (% out of 257 cases), the number of
unique species per cause, and the number of ecozones for which the cause of dermatitis was reported
in. For further analysis, causes with ‘*’ were combined into ‘Other’ category.
Percentage Definitive Species per
Cause Ecozone
Diagnosis (n) Cause
Apicomplexan * 1.2% (3) 2 1
Bacteria 16.3% (42) 29 6
Bacteria & Fungus * 0.8% (2) 1 1
Diptera * 1.2% (3) 3 2
Ectoparasite (unknown) * 0.4% (1) 1 1
Animals 2021, 11, x Fleas 0.8% (2) 2 1 7 of 20
Fungus 9.0% (23) 15 3
Louse * 0.8% (2) 2 2
Mineral deficiency * 0.4% (1) 1 1
Dermatitis
Mite was reported in 10821.4%
different
(55) mammal species, 34totaling 4118 individuals.
5
Wild, Mite
free-living
& Fungusmammals
* had a higher
0.4% frequency
(1) of reported1dermatitis cases (57.2%,
1 n
= 147,Mite
69 species),
& Nematode compared
* to wild0.4%
animals
(1) that were brought 1 into or born in captivity
1
(33.07%, Nematode
n = 85, 51 species), and those2.7% under
(7) 6
laboratory conditions (9.73%, n 2= 25, 12
Plant * 1.6% (4) 4 2
species) (Figure 2). The highest proportion of reported cases of dermatitis for free-living
Protozoa * 0.4% (1) 1 1
wildlife was caused by mites (Figure 2). By contrast, unknown causes of dermatitis in
Tick 2.3% (6) 6 2
captive wildlife
Unknown had the highest proportion
23.7% (61) of cases. Interestingly,
35 wildlife5 from a
laboratory Virus
setting had no ‘other’ 16.3%
causes,
(42) and the primary 15 cause of dermatitis
4 was
unknown
* Other. (Figure 2).
Figure 2. Proportion of the top five causes of dermatitis reported in terrestrial mammalian wildlife, summarized into each
Figure 2. Proportion of the top five causes of dermatitis reported in terrestrial mammalian wildlife, summarized into each
captive or free-ranging group. Captivity status consists of wild free-living, wild-captive and wild-laboratory. The percentage
captive or free-ranging group. Captivity status consists of wild free-living, wild-captive and wild-laboratory. The
of definitive dermatitis causes reported in wildlife is shown for each group.
percentage of definitive dermatitis causes reported in wildlife is shown for each group.
The 257 wildlife dermatitis cases spanned six biogeographical realms (hereafter ‘eco-
TheThe
zone’). 257Nearctic
wildlifehad
dermatitis
the highestcases spanned
number six biogeographical
of reported realms
cases of dermatitis (hereafter
(54.9%, n = 141,
‘ecozone’). The Nearctic had the highest number of reported cases of dermatitis
59 species), followed by Palearctic (29.2%, n = 75, 37 species), Australasia (9.3%, (54.9%, n
n = 24,
=18
141, 59 species), followed by Palearctic (29.2%, n = 75, 37 species), Australasia (9.3%,
species), Neotropics (4.3%, n = 11, 9 species), Afrotropics (1.9%, n = 5, 4 species), and n =
24, 18 species), Neotropics (4.3%, n = 11, 9 species),
Indomalaya (0.4%, n = 1, 1 species) (Figure 3). Afrotropics (1.9%, n = 5, 4 species), and
Indomalaya (0.4%, n = 1, 1 species) (Figure 3).Animals2021,
Animals 11,x1691
2021,11, 87ofof2019
Figure 3. The total number of reported dermatitis cases split into captivity status (wild free-living, wild captive and wild
Figure 3. The total number of reported dermatitis cases split into captivity status (wild free-living, wild captive and wild
laboratory), for five of the six biogeographical realms (ecozone) where mammalian wildlife dermatitis cases were reported in
laboratory), for five of the six biogeographical realms (ecozone) where mammalian wildlife dermatitis cases were reported
the literature, with an ecozone area (million km2 ). There was one wild captive case recorded for the Indomalaya (7.5 m km2 )
in the literature, with an ecozone area (million km2). There was one wild captive case recorded for the Indomalaya (7.5 m
ecozone,
km which
2) ecozone, is not
which is displayed.
not displayed.
4.4.Etiological
EtiologicalAgents
AgentsResponsible
Responsiblefor forthe
theCauses
CausesofofDermatitis
Dermatitisacross
acrossMammalian
Mammalian
Wildlife Species
Wildlife Species
There were
There were over
over 6060causal agents
causal of dermatitis
agents reported
of dermatitis in thein108
reported mammalian
the wildlife
108 mammalian
species (Table S4). Due to diagnostic features, identification of some pathogens
wildlife species (Table S4). Due to diagnostic features, identification of some pathogens could
only be narrowed to the family or genus, or in some cases were reported
could only be narrowed to the family or genus, or in some cases were reported as an as an unknown
agent (e.g., ‘unknown nematode’). The bacterial pathogen Dermatophilus congolensis had
unknown agent (e.g., ‘unknown nematode’). The bacterial pathogen Dermatophilus
caused dermatitis in the highest number of wildlife species (n = 18) and across the greatest
congolensis had caused dermatitis in the highest number of wildlife species (n = 18) and
number of wildlife orders (Table 3); followed by the Parapoxvirus genus (n = 13), and the
across the greatest number of wildlife orders (Table 3); followed by the Parapoxvirus genus
mite species Demodex and Notoedres, both causing dermatitis in eight species of wildlife
(n = 13), and the mite species Demodex and Notoedres, both causing dermatitis in eight
(Table 3). All other causal agents caused dermatitis in four or less species (Table S4).
species of wildlife (Table 3). All other causal agents caused dermatitis in four or less
species (Table S4).
Table 3. The top seven causal agents of dermatitis in wildlife species, with all other causes effecting
four or less species (Table S4). For each causal agent, the etiological category, the number of species
Table 3. The top seven causal agents of dermatitis in wildlife species, with all other causes effecting
the or
four agent
lesswas reported
species (TabletoS4).
cause
Fordermatitis in,agent,
each causal and the
thenumber of orders
etiological is shown.
category, the number of species
the agent was reported to cause dermatitis in, and the number of orders is shown.
Causal Agent Category Species Orders
Causalcongolensis
Dermatophilus Agent Category
Bacteria 18Species Orders
6
Parapoxvirus (genus)
Dermatophilus congolensis Virus
Bacteria 13 18 26
Demodex sp. (genus)
Parapoxvirus (genus) Mite Virus 8 13 42
Notoedres sp. (genus) Mite 8 3
Demodex
Sarcoptes sp. (genus)
scabiei Mite Mite 7 8 24
Notoedres sp.
Staphylococcus sp. (genus)
(genus) BacteriaMite 7 8 63
Malassezia sp. (genus)
Sarcoptes scabiei FungusMite 6 7 22
Staphylococcus sp. (genus) Bacteria 7 6
5. CausesMalassezia sp. (genus)
of Dermatitis across Wildlife OrdersFungus 6 2
Artiodactyla had the highest number of dermatitis cases reported (n = 71, 27.6%,
5 ecozones), with viruses being the greatest cause of dermatitis in this order (Figure 4a).Animals 2021, 11, 1691 8 of 19
Animals 2021, 11, x 9 of 20
Semi-aquatic Carnivora had the lowest number of cases reported (n = 16; 6.2%; 2 ecozones),
with fungus being their most common cause (Figure 4b). Terrestrial Carnivora was second
highest (n = 59; 23.0%; 5 ecozones), with mite cases being most prevalent (Figure 4c).
5. Causes of Dermatitis across Wildlife Orders
Rodentia had 36 dermatitis cases reported (14.0%; 3 ecozones), with viruses being the
Artiodactyla
greatest had the highest
cause of dermatitis in this number
mammaloforder
dermatitis
(Figurecases reported had
4d). Primates (n =2371,dermatitis
27.6%, 5
ecozones), with (8.9%;
cases reported viruses4 ecozones),
being the greatest
and thecause of dermatitis
most prominent in this
causes order (Figure
reported 4a).
were either
Semi-aquatic Carnivora had the lowest number of cases reported (n
bacteria or unknown (Figure 4e). Diprotodontia had 19 dermatitis cases reported (7.4%;= 16; 6.2%; 2
ecozones), with fungus being their most common
2 ecozones), often with an unknown cause (Figure 4f). cause (Figure 4b). Terrestrial Carnivora
was second
Primates highest
had the(nhighest
= 59; 23.0%;
number5 ofecozones), with
species and mite
cases cases being
of dermatitis formost prevalent
wild laboratory
(Figure 4c). Rodentia had 36 dermatitis cases reported (14.0%; 3 ecozones),
mammals (Figure 4e). Terrestrial Carnivora had the highest number (14) of unknown with viruses
being the greatest
dermatitis causes.cause of dermatitis
Interestingly, in this
mites havemammal
been shownorderto(Figure
cause 4d). Primates
dermatitis had 23
across all
dermatitis cases
orders except reported (8.9%;
semi-aquatic 4 ecozones),
Carnivora. Bacteriaand
wasthe most prominent
responsible causescases
for dermatitis reported
in all
were
orderseither
exceptbacteria or unknown
Diprotodontia, (Figure reported
with viruses 4e). Diprotodontia
as a cause ofhad 19 dermatitis
dermatitis in only cases
three
reported (7.4%;
(Figure 4). 2 ecozones), often with an unknown cause (Figure 4f).
(a) Artiodactyla (b) semi-aquatic Carnivora
(c) terrestrial Carnivora (d) Rodentia
Figure 4. Cont.Animals
Animals2021,
2021,11,
11,x1691 10 9ofof2019
(e) Primates (f) Diprotodontia
Wild Free-living Wild Captive Wild Laboratory
Figure
Figure4.4.The
Thecauses
causesofofdermatitis
dermatitisdiagnosed
diagnosedforforeach
eachwildlife
wildlifeorder,
order,and
andfor
foreach
eachcaptivity
captivitystatus
status(wild
(wildfree-living,
free-living,wild
wild
captive,
captive,and
andwild
wildlaboratory),
laboratory),plotted
plottedagainst
againstthe
thenumber
numberofofdefinitive
definitivedermatitis
dermatitisdiagnosis/cases:
diagnosis/cases:(a,c)
(a,c)0–25
0–25cases;
cases;(b,d–e)
(b,d–f)
0–15
0–15cases.
cases.
Primates had
6. Threatened the Reported
Species highest number of species and cases of dermatitis for wild
with Dermatitis
laboratory mammals (Figure 4e). Terrestrial
Of the 108 wild mammal species reported Carnivora
as havinghaddermatitis,
the highest65.7%
number (n =(14) of
71) are
unknown
regarded dermatitis causes. Interestingly,
as ‘Least Concern’ by the IUCN (2021)mites andhaveanother
been shown
10.2% (n to =cause
11) aredermatitis
regarded
across
as ‘Nearall orders exceptThese
threatened’. semi-aquatic
two groups Carnivora.
have been Bacteria was by
evaluated responsible
the IUCNfor as dermatitis
species not
cases
under in immediate
all orders except
threatDiprotodontia,
of extinction and, withtherefore,
viruses reported as a cause
we omitted these of82dermatitis
species fromin
only three (Figure 4).
further analysis on conservation concerns. We also omitted two species from the bat family
Vespertilionidae, and one species of goral, Naemorhedus griseus, due to insufficient data
6.onThreatened
their IUCN Species Reported
conservation with(2.8%,
status Dermatitis
n = 3). The other 21.3% (n = 23) of species are
classified
Of theby 108IUCN
wildas ‘Vulnerable’
mammal species(12%, n = 13),
reported as‘Endangered’ n = 5) (n
(4.6%, 65.7%
having dermatitis, or ‘Critically
= 71) are
Endangered’ (4.6%, n = 5) (Table 4). There were 45 cases of dermatitis
regarded as ‘Least Concern’ by the IUCN (2021) and another 10.2% (n = 11) are regarded reported across the
23 threatened species: nine cases of Critically Endangered (CR),
as ‘Near threatened’. These two groups have been evaluated by the IUCN as species not seven cases of Endangered
(EN), immediate
under and 29 casesthreat
of Vulnerable (VU) and,
of extinction (Tabletherefore,
3). There wewere no species
omitted thesethat
82 were
speciesclassified
from
as Extinct,
further Extinct
analysis oninconservation
the Wild, or Regionally
concerns. We Extinct
also reported
omitted having dermatitis.
two species from the bat
familyTerrestrial Carnivora
Vespertilionidae, andhad onethe highest
species number
of goral, of reported
Naemorhedus dermatitis
griseus, due tocases (n = 16),
insufficient
in six threatened species, followed by Artiodactyla with reported
data on their IUCN conservation status (2.8%, n = 3). The other 21.3% (n = 23) of species cases (n = 9) in four
threatened species (Table 4). Dermatitis cases were reported
are classified by IUCN as ‘Vulnerable’ (12%, n = 13), ‘Endangered’ (4.6%, n = 5) or more often in threatened
species outside
‘Critically of their(4.6%,
Endangered’ endemic n = 5)ecozone and
(Table 4). within
There captivity
were 45 cases(57.8%, n = 26)reported
of dermatitis (Table 4).
There was no consistent cause of dermatitis identified for the 45 cases
across the 23 threatened species: nine cases of Critically Endangered (CR), seven cases of reported across all
threatened species (Table S5). In threatened species, treatment of
Endangered (EN), and 29 cases of Vulnerable (VU) (Table 3). There were no species that dermatitis was attempted
in 26classified
were cases (58%), which consisted
as Extinct, Extinct inofthe medical
Wild, intervention
or RegionallyforExtinct
the cure of the cause
reported havingof
dermatitis
dermatitis. (e.g., antibiotics; ivermectin), or for mitigation of clinical signs (e.g., removal of
lesions) if the cause was chronic (e.g., Feline Herpes Virus). Treatment was successful in
Table 4. International Union most instances (nof=Nature’s
for Conservation 17) and(IUCN)
was not attempted
Red in 19 cases
List of threatened wild(42%)
mammal(Table S5). reported
species
as having dermatitis. The 23 species categorized as ‘Critically Endangered’ (CR), ‘Endangered’ (EN), and ‘Vulnerable’
(VU) are shown, including their order and total number of cases. The number of dermatitis cases within endemic ecozones
are shown for each species and the number of cases within non-endemic ecozones. Both ecozone categories are separated
into the following captivity statuses of: Wild Captive (WC), Wild Free-living (WFL) and Wild Laboratory (WL). * WFL has
one reported case within a non-endemic ecozone (*), and WL has no reported cases across non-endemic ecozones, so the
columns have been removed to simplify the table.
Non-Endemic
Threatened Total Endemic Ecozone Cases
IUCN (2021) Threatened Species Order Ecozone Cases *
Category Cases
WFL WC WL WCAnimals 2021, 11, 1691 10 of 19
Table 4. International Union for Conservation of Nature’s (IUCN) Red List of threatened wild mammal species reported as
having dermatitis. The 23 species categorized as ‘Critically Endangered’ (CR), ‘Endangered’ (EN), and ‘Vulnerable’ (VU)
are shown, including their order and total number of cases. The number of dermatitis cases within endemic ecozones are
shown for each species and the number of cases within non-endemic ecozones. Both ecozone categories are separated
into the following captivity statuses of: Wild Captive (WC), Wild Free-living (WFL) and Wild Laboratory (WL). * WFL has
one reported case within a non-endemic ecozone (*), and WL has no reported cases across non-endemic ecozones, so the
columns have been removed to simplify the table.
Non-Endemic
Threatened Endemic Ecozone Cases
IUCN (2021) Threatened Species Order Total Cases Ecozone Cases *
Category
WFL WC WL WC
terrestrial
Canis rufus (red wolf) CR 1 1
Carnivora
Dasyprocta mexicana (Mexican agouti) CR Rodentia 1 1
Diceros bicornis (black rhinoceros) CR Perissodactyla 5 2 3
terrestrial
Mustela lutreola (European Mink) CR 1 1
Carnivora
Pongo pygmaeus pygmaeus (Northwest Bornean
CR Primates 1 1
orangutan)
terrestrial
Ailurus fulgens (red panda) EN 2 2
Carnivora
Other
Elephas maximus (Asian Elephant) EN 2 1 1
(Elephantidae)
Pentalagus furnessi (Amami rabbit) EN Lagomorpha 1 1
Petrogale persephone (Proserpine rock wallaby) EN Diprotodontia 1 1
Symphalangus syndactylus (siamang) EN Primates 1 1
terrestrial
Acinonyx jubatus (cheetah) VU 5 1 4
Carnivora
Alouatta palliata (Mantled Howler Monkey) VU Primates 1 1
Budorcas taxicolor tibetana (Sichuan takin) VU Artiodactyla 1 1
Hippopotamus amphibius (Nile hippopotamus) VU Artiodactyla 3 3
Lagothrix lagotricha (woolly monkey) VU Primates 1 1
Macaca fascicularis (crab-eating macaque) VU Primates 2 2*
Petrogale penicillata (brush-tailed rock-wallaby) VU Diprotodontia 1 1
Phascolarctos cinereus (koala) VU Diprotodontia 1 1
Rangifer tarandus (caribou) VU Artiodactyla 4 1 2 1
Rhinoceros unicornis (Indian rhinoceros) VU Perissodactyla 2 2
Rusa unicolor (Sambar) VU Artiodactyla 1 1
terrestrial
Tremarctos ornatus (Andean bear) VU 3 3
Carnivora
terrestrial
Ursus maritimus (polar bear) VU 4 2 1 1
Carnivora
Total 45 10 7 1 26(*1)
7. Discussion
Overall, there were more than 60 causal agents of dermatitis reported in wildlife,
showing that this clinical sign can manifest from a variety of causes. However, the highest
single proportion of reported cases was of an unknown cause. This may be since identifying
the causal agent is recognized as a key challenge in the literature, and there are a variety of
sampling techniques needed to correctly detect the dermatitis agent. Of the 60 definitive
causes of dermatitis, mites were the most common across all species. Bacteria were the
second highest cause of dermatitis across wild mammalian species, and this was driven by
Dermatophilus congolensis (causing dermatophilosis) infection. There were a higher number
of cases reported in free-ranging wildlife, and captivity had a greater role to play for the
development of dermatitis in IUCN threatened species. However, the causes of dermatitis
are rarely reported as a conservation issue for threatened species. Reporting biases are
recognized in the ecozone Nearctic and the mammalian orders of terrestrial Carnivora and
Artiodactyla.
7.1. The Main Causes of Dermatitis in Mammalian Wildlife: Mites, Bacteria and Viruses
Due to the wide taxonomic range of mites’ (such as Sarcoptes scabiei) host species,
it is unsurprising that they account for the highest percentage of diagnosed dermatitis
cases in the greatest number of wildlife species [35–37]. Mites were the predominant
cause of dermatitis reports in five of the six mammal orders, and, across these, over
15 genera of mites were represented with the top three: Demodex sp., Notoedres sp. and
Sarcoptes scabiei. Demodex mites are commensal, found in hair follicles across an arrayAnimals 2021, 11, 1691 11 of 19
of taxa, including humans. However, under favorable environments, they can become
opportunistic and an over proliferation can cause the skin condition demodicosis, which
can cause dermatitis [38]. Conversely, the Notoedres sp. and Sarcoptes scabiei are both from
the Sarcoptidae family, and are highly contagious pathogens that can infest a wide variety
of animal orders [35–37]. Notoedres sp. can cause notoedric mange, and is associated with
the development of dermatitis, particularly in rodents and felids, which was supported by
the findings in our review [37]. In fact, both mites can cause an array of dermatological
signs, from alopecia, inflammation, to even secondary infections and death. S. scabiei causes
sarcoptic mange and is an emerging infectious disease for some species, exerting animal
welfare and conservation pressures [35,36]. However, given the wide host range of this
mite species, it was surprising this mite was not the leading causal agent in our review.
This may be because dermatitis is not a representative clinical sign of mange, or clinical
signs were not specifically mentioned in S. scabiei studies.
Given their global ubiquity and wide host range, it was unsurprising that viruses and
bacteria were the second highest causative agents of dermatitis cases [39,40]. Viruses were
mostly represented by the Parapoxvirus (genus), in Artiodactyla and Rodentia. High report-
ing of this cause may be since the Parapoxvirus is found worldwide and can be transmitted
between domestic mammals and wildlife in the Artiodactyla order [41]. The most common
bacteria species was Dermatophilus congolensis and bacteria from the genus Staphylococcus.
Some bacteria, such as Staphylococcus sp., are a part of normal skin microflora, and certain
host and environmental factors may cause these commensal bacteria to become problem-
atic and cause skin conditions, such as atopic dermatitis [42]. Dermatophilus congolensis
(causing dermatophilosis) bacterium caused dermatitis across the most species; these bac-
teria are found globally, have a wide host range, and the epidemiology is broadly known
in the literature [24,39,43]. Dermatophilosis has caused dermatitis in species as diverse
as the meadow jumping mouse (Zapus hudsonius) [29] and ground squirrels (Urocitellus
columbianus columbianus) [44] from the order Rodentia; owl monkey (Aotus trivirgatus) [45]
and orangutans (Pongo pygmaeus pygmaeus) [26] from Primates; polar bears (Ursus mar-
itimus) [46] and racoons (Procyon lotor) [47] from terrestrial Carnivora; and white-tail deer
(Odocoileus virginianus) [48] from Artiodactyla, to name a few.
7.2. Captivity Status and Dermatitis in Wild Mammals
Dermatitis was reported to occur in wild free-living mammals more often than their
wild laboratory or captive counterparts. This may be due to under reporting of dermatitis
in captive wildlife, treatment regimens for wildlife in captivity, or biases towards the report-
ing of free-living individuals. Dermatological problems are common in captive wildlife,
ranging from secondary infection due to poor husbandry to self-inflicted lesions subse-
quent to stereotypic behaviour [49,50]. Therefore, it is possible due to their commonality,
skin problems are treated without being reported in the literature; and skin issues in wild
animals are deemed more important. Furthermore, dermatological issues in wild captive
animals may be treated before the signs of disease become advanced enough to warrant
reporting, since individuals within captivity or laboratory settings are often quarantined
and treated for common diseases as a precaution and are subject to routine examinations
for signs of disease [51,52], whereas free-living individuals may be more likely to show
later stages of dermatitis clinical signs since early treatment is unlikely.
Wild free-living mammals may be more likely to be reported with dermatitis or show
later stages of clinical signs since: (i) there are no preventative steps in stopping spread
and limited veterinary intervention; (ii) they come into contact with many more species
and individuals which might have pathogen causing dermatitis (such as other mammals,
domestic animals and livestock) [53]; and (iii) they have unregulated environmental factors,
which vary from contact with unusual plants [54] to opportunistic pathogens [55].
Primates had the highest reported cases of dermatitis for wild laboratory, owing
to their regular use as an experimental subject. For wild laboratory mammals, where
almost half of the dermatitis causes were ‘unknown’, it is likely that commensal andAnimals 2021, 11, 1691 12 of 19
non-pathogenic parasites were a prevailing problem, due to stress associated with an
unnatural, confined environment [51]. In fact, such speculation was made for both captive
and laboratory animals in Van Horn et al. [56] and Steinmetz et al. [6] where unknown
dermatitis was presumed psychogenic of origin.
7.3. Threatened Species with Dermatitis
Generally, reported cases of dermatitis in the literature largely described the occurrence
of dermatitis in the species, or in a particular part of a species’ range, for the first time.
There were few reports of dermatitis being a primary concern for the conservation of a
species, despite our identification of 23 threatened species reported as having dermatitis.
The causes of dermatological lesions reduce fitness and thus constitute another pressure on
threatened populations, with many species driven to extinction often due to compounding
anthropogenic activities [57]. However, many threatened species’ articles only briefly
mentioned causes of dermatitis as a conservation concern or that the mammal is endangered
(e.g., [5,46,58]). Reports which focused on dermatitis causes as a conservation threat
for a species, for example Munson et al. [5], Witte et al. [59] and Van Horn et al. [56],
discussed dermatitis induced health problems and mortality could affect captive population
sustainability and husbandry management. However, overall, there was no pattern in
reporting treatment success or failure for threatened species. Pathogens causing dermatitis
were also identified as a conservation threat to the red squirrel (Sciurus vulgaris), San
Joaquin Kit Fox (Vulpes macrotis mutica), and Amargosa vole (Microtus californicus scirpensis)
despite these mammals not being identified by the IUCN as at-risk species [21,23,60,61].
Therefore, it is important to consider that (1) some mammals may not have been classified as
threatened when dermatitis was reported in the past, and (2) some species and subspecies
may be missed by the IUCN and, as the classification is updated, more species may be
added to the threatened categories in the future.
The threatened species cases in our review show that 33 dermatitis cases (total of 45)
were in captivity. This may be due to the routine observations for captive individuals,
compared to their free-living counterparts. However, we determine that there may be
multiple compounding factors which may cause threatened species in captivity to be more
likely to exhibit dermatitis, such as: lack of genetic diversity, added psychological stress
in captivity [56,62], exposure to alien pathogens, and environmental exacerbations [63].
Loss of genetic diversity is common in many threatened species, potentially lowering
their resistance to diseases and inflammatory conditions, making them more prone to
agents which can cause dermatitis [64–66]. Loss of genetic diversity may be one of the
reasons terrestrial Carnivora had the highest number of threatened species dermatitis cases
reported, because many lack the genetic diversity of other mammals [65,67]. Low genetic
diversity and small population size are also a conservation concern, particularly for the
management of breeding programs, and act in synergy with disease and a species’ capacity
to adapt to changing environmental conditions [64,66,68,69]. Conversely, large populations
of nonthreatened individuals have a greater ability to adapt to captivity stressors [63].
Physiological responses to stress, or stress induced by environmental changes, might also
manifest as dermatitis in threatened species in captivity via immune suppression [62,63,67].
For example, Munson et al. [65] describe both captive and free-ranging cheetahs having
the same genetic diversity; however, captive cheetahs had worse reactions to viral infec-
tions and severe inflammatory reactions to common infections, suggesting that the local
environment is important in determining health trajectories of individuals, beyond just
genetic susceptibility. Additionally, since the majority (70%) of dermatitis cases for captive
threatened species were located outside of their endemic range; captive stressors may be
exacerbated for threatened species due to exposure to alien pathogens and sub-optimal
environmental conditions [69–71]. It is well known that the introduction of wild non-native
species to foreign geographic ranges has increased potential for disease emergence and
outbreaks [71,72].Animals 2021, 11, 1691 13 of 19
For several species, the development of dermatitis as a reaction to disease is associated
with genetic and behavioral features [73–75]. This is particularly true of rhinoceroses,
which are especially prone to skin diseases and lesions [5]. Dermatitis manifestation
in rhinoceroses was not due to one specific bacterial or viral infection, but was instead
associated with concurrent diseases or events, where dermal erosions or ulcers are the
first clinical signs of underlying health issues [5,76]. Determining the reasons why some
threatened species may be more susceptible to dermatological diseases can help inform
management practices and husbandry behaviors within captivity.
7.4. Reporting Bias for Orders of Mammalian Wildlife and across Ecozones
Our synthesis might be impacted by a reporting bias for dermatitis in the mammalian
orders of Artiodactyla and terrestrial Carnivora. These orders have similar and lower
number of species, at about 220 and 268, respectively, compared to Primates (300) and
Rodentia (1500). We suspect that, with a higher number of species, there is a greater chance
of dermatitis occurring and being opportunistically observed in that mammalian order.
Potential observation bias for reporting dermatitis in larger animals may be related to
chance occurrence, since dermatitis is easier to see in larger animals [77,78] or reported
due to relative-attention bias [79]. Furthermore, it is known that historical biodiversity
records for charismatic species, particularly large mammals, have reporting biases [80,81].
This may also explain the high number of reported dermatitis cases in both terrestrial
Carnivora and Artiodactyla, and less for Rodentia, despite the order Rodentia having about
six-fold more species. Additionally, Artiodactyla species are genetically similar (or, in some
cases, used as) agricultural animals [82,83], or game species [48]. Clegg et al. [84] reported
dermatitis for the first time in wild elk; elk potentially contracted the bacterial species
Treponema from livestock pastures and could now be a reservoir for domestic livestock and
other wild animals. This is especially the case of the genus Parapoxvirus, with articles on
this dermatitis causing agent focusing on domestic livestock species or human infections
from wildlife [41,85]. This implies that Artiodactyla species’ proximity to humans and
the potential for economic consequences might also explain why this order is the primary
focus of dermatitis reports.
Biogeographic realms have been used as the broadest scale for identifying and plan-
ning the conservation of species [86,87] and biotic processes [88,89]. However, applying
macroecological generalities to complex systems such as infectious disease has been viewed
as an unresolved challenge and, until recently, biogeography has rarely been included
in management of human or veterinary health [90,91]. For certain dermatitis causes, an
ecozone’s environmental attributes could inhibit or exacerbate dermatitis severity, spread
of causes and growth of lesions. Therefore, there is no doubt that biogeographical analysis
offers a potentially important explanatory role that can provide insight into spatial pat-
terns of multiple systems [90,92]. However, our synthesis on the literature to date suggest
that funding and economics play a greater role in the reporting of dermatitis in ecozones.
Indeed, our overview of this research suggests that opportunistic reports have led to an
artificial trend of dermatitis in the Nearctic [79,93]. For example, dermatophilosis is more
likely to occur in relatively low altitude areas with tropical and subtropical climates [39].
Therefore, in theory, dermatophilosis would be more likely to be reported in the Afrotropic
and Neotropic ecozones [26]; however, more cases of dermatophilosis were reported within
the Nearctic. Geographical bias in reporting has been found in other studies [94–96],
supporting the potential for a skew towards reports in the Nearctic ecozone.
7.5. Limitations of Reviewing Clinical Signs of Diseases or Irritants
Our review provides a valuable synthesis of the use of the term dermatitis and patterns
in mammalian wildlife. Indeed, such syntheses on common causes of dermatitis have
been produced for domestic and livestock animals [97,98]; however, in wildlife, focus has
been primarily on either (i) a certain type of agent affecting the wildlife, e.g., parapoxvirus
or Neospora caninum infection in wildlife (e.g., [41,99,100]) or (ii) on pathogens affectingAnimals 2021, 11, 1691 14 of 19
individual species (e.g., captive pinnipeds) which are, by chance, or perhaps due to visual
dermatological conditions (e.g., [18,59,101]). Our unique synthesis, while not completely
exhaustive, is representative of published information across different mammalian wildlife
groups for a clinical sign (dermatitis), which has, to date, been overlooked but is important
to consider.
However, we have identified several limitations in reviewing clinical signs of pathogen
agents. Firstly, the variable use of clinical signs in diseases or irritants is a key challenge in
undertaking syntheses. For example, histopathological descriptions of dermatitis may be
used without applying the term explicitly. Due to this, the search term for dermatitis could
underestimate the number of articles with dermatitis, since it does not capture cases with
‘dermatitis like’ clinical signs.
Furthermore, the term dermatitis may not be used in the title, abstract or key words
because it is: (i) not a key feature of the histopathology of that pathogen; (ii) unclearly
defined, such as a dermatitis like term; or (iii) the clinical signs are not mentioned at all,
most likely because it is a well-known pathogen. The latter may be the case for Sarcoptic
mange, caused by the mite Sarcoptes scabiei in over 100 mammalian species. However, we
only found S. scabiei as the cause of dermatitis in seven wildlife species in our review, and,
therefore, dermatitis is either not a term used for normally describing mange, or, because it
is a well-known pathogen, the histological signs are not described in the abstract. In another
example, White Nose Syndrome (WNS) in bats has been described as having histologically
identifiable infiltrative fungal dermatitis [22]. However, we had no articles with WNS in
our synthesis. Two articles in our review were screening for WNS in bats; however, they
describe dermatitis as the main clinical signs of other pathogen infections [55,102].
Conversely, the clinical signs of disease would be more likely to be within the title
and abstract if the clinical sign in question is unknown, since the dermatological origin
is not identified. To combat this, we suggest that the clinical aspects of the skin diseases
and irritation be described in the abstract of papers, regardless of whether the pathogen
is well known. Despite limitations of reporting of clinical signs of skin diseases and
irritants, our synthesis identifies the overall causes and patterns of dermatitis in wild
mammalian species.
8. Conclusions
This review has identified that, overall, there seems to be bias towards reporting
dermatitis cases when the cause is unknown or when presented in a species for the first time.
For some species, it was noted that the underlying causal agents were first investigated due
to the visibility of dermal lesions (e.g., [5,78]). Through the valuable compendium of reports,
we have additionally identified that, when the causal agent of dermatitis is unknown,
reports may be more likely to include dermatitis within the title and abstract (since the
dermatological symptoms are in question and the origin not identified). Furthermore,
the search term for dermatitis could also underestimate the number of articles and cases
showing dermatitis, since the term might not be included in the title or abstract of articles
dealing with a disease or agent for which dermatitis is usually just one of several possible
manifestations. Conversely, for threatened species with dermatitis, 15 cases from 45 were of
unknown causes (Table S5). This is perhaps because the identification of unknown causes
of dermatitis, and the successful treatment of dermatitis lesions, regardless of cause, are of
particular interest to threatened species given their parlous conservation status.
In general, dermatitis is rarely reported as a conservation issue; however, we have
discovered that some threatened species may be more likely to exhibit dermatitis in cap-
tivity, and, for others, diseases often manifest, at least in part, as dermatitis. This review
highlights that, in some cases, species of concern are declining due to specific reasons that
are clinically revealed as dermatitis. However, dermatitis reporting in wild semi-aquatic
and terrestrial mammals remains subject to many biases. As such, future case studies of
diseases should: (i) document the main clinical signs and manifestations of the disease or
causative agent in the abstract of reports, and (ii) encompass a range of dermatologicalAnimals 2021, 11, 1691 15 of 19
conditions, since an animal may be suffering a form of dermatitis but was classified as
another skin disorder (e.g., dermatophilosis). With our suggestions, we can bridge cross-
disciplinary gaps between veterinary, genetics, captive management, and conservation,
and further research can determine common spatial patterns of dermatological diseases for
wild mammals.
Supplementary Materials: The following are available online at https://www.mdpi.com/article/
10.3390/ani11061691/s1, Search terms S1: The search terms used to identify the relevant literature
in each database, Table S2: Complete dataset of all 216 articles that reported wildlife dermatitis,
Table S3: All individually reported dermatitis cases for each order not presented in the synthesis,
Table S4: Etiological agents responsible for the causes of dermatitis across mammalian wildlife
species, Table S5: Each reported threatened species dermatitis cases and their corresponding IUCN
(2021) threatened categories, concurrent disease, dermatitis treatment, and whether the treatment
resolved dermatitis.
Author Contributions: Conceptualization, E.M.R., B.W.B., S.C. and J.C.B.; methodology and formal
analysis, E.M.R. and J.C.B.; data curation, E.M.R.; writing—original draft preparation, E.M.R.;
writing—review and editing, E.M.R., B.W.B., S.C. and J.C.B.; supervision, B.W.B., S.C. and J.C.B.;
funding acquisition, B.W.B. and S.C. All authors have read and agreed to the published version of
the manuscript.
Funding: This research was funded by the Australian Research Council, Grant Nos. FL160100101
and LP180101251, and the University of Tasmania CoSE Research Training Program.
Institutional Review Board Statement: Not applicable.
Data Availability Statement: The data presented in this study are available in the Supplementary
Materials section.
Conflicts of Interest: The authors declare no conflict of interest.
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